			Home About us Contact

Glutathione Biosynthesis (glutathione + biosynthesis)

Distribution by Scientific Domains

Life Sciences	83%

Selected Abstracts

The redox switch of ,-glutamylcysteine ligase via a reversible monomer,dimer transition is a mechanism unique to plants

THE PLANT JOURNAL, Issue 6 2008
Roland Gromes
Summary In plants, the first committed enzyme for glutathione biosynthesis, ,-glutamylcysteine ligase (GCL), is under multiple controls. The recent elucidation of GCL structure from Brassica juncea (BjGCL) has revealed the presence of two intramolecular disulfide bridges (CC1, CC2), which both strongly impact on GCL activity in vitro. Here we demonstrate that cysteines of CC1 are confined to plant species from the Rosids clade, and are absent in other plant families. Conversely, cysteines of CC2 involved in the monomer,dimer transition in BjGCL are not only conserved in the plant kingdom, but are also conserved in the evolutionarily related ,- (and some ,-) proteobacterial GCLs. Focusing on the role of CC2 for GCL redox regulation, we have extended our analysis to all available plant (31; including moss and algal) and related proteobacterial GCL (46) protein sequences. Amino acids contributing to the homodimer interface in BjGCL are highly conserved among plant GCLs, but are not conserved in related proteobacterial GCLs. To probe the significance of this distinction, recombinant GCLs from Nicotiana tabacum (NtGCL), Agrobacterium tumefaciens (AtuGCL, ,-proteobacteria) and Xanthomonas campestris (XcaGCL, ,-proteobacteria) were analyzed for their redox response. As expected, NtGCL forms a homodimer under oxidizing conditions, and is activated more than threefold. Conversely, proteobacterial GCLs remain monomeric under oxidizing and reducing conditions, and their activities are not inhibited by DTT, despite the presence of CC2. We conclude that although plant GCLs are evolutionarily related to proteobacterial GCLs, redox regulation of their GCLs via CC2-dependent dimerization has been acquired later in evolution, possibly as a consequence of compartmentation in the redox-modulated plastid environment. [source]

Differential targeting of GSH1 and GSH2 is achieved by multiple transcription initiation: implications for the compartmentation of glutathione biosynthesis in the Brassicaceae

THE PLANT JOURNAL, Issue 1 2005
Andreas Wachter
Summary The genome of Arabidopsis thaliana reveals that in this species the enzymes of glutathione biosynthesis, GSH1 and GSH2, are encoded by single genes. In silico analysis predicts proteins with putative plastidic transit peptides (TP) for both genes, but this has not been experimentally verified. Here we report a detailed analysis of the 5,ends of GSH1 and GSH2 mRNAs and demonstrate the subcellular targeting of the proteins encoded by different transcript types. GSH1 transcript analysis revealed two mRNA populations with short and long 5,-UTRs, respectively, both including the entire TP sequence. The ratio of long/total GSH1 transcripts was subject to developmental regulation. Transient transformation experiments with reporter gene fusions, bearing long or short 5,-UTRs, indicated an exclusive targeting of GSH1 to the plastids. Corroborating these results, endogenous and ectopically expressed GSH1 proteins were always present as a single polypeptide species with the size expected for correctly processed GSH1. Finally, the plastidic GSH1 localization was confirmed by immunocytochemistry. Similar to GSH1, multiple transcript populations were found for GSH2. However, here the prevalent shorter transcripts lacked a complete TP sequence. As expected, the large (but less abundant) transcript encoded a plastidic GSH2 protein, whereas GSH2 synthesized from the shorter transcript was targeted to the cytosol. The implications of the results for the compartmentation and regulation of GSH synthesis are discussed. [source]

Prospects for enhancement of the soluble antioxidants, ascorbate and glutathione

BIOFACTORS, Issue 2-4 2001
Christine H. Foyer
Ascorbic acid (vitamin C) and the tripeptide thiol, glutathione , -glutamyl cysteinyl glycine (glutathione) are the major low molecular weight soluble antioxidants in plant cells. The pathway of glutathione biosynthesis is similar in animals and plants while that of ascorbate biosynthesis differs considerably between the two kingdoms. The potential for obtaining substantial constitutive changes in the tissue contents of these antioxidants by manipulation of the biosynthetic enzymes has been demonstrated. Moreover, the concentrations of ascorbate and glutathione are greatly modified in response to a variety of environmental triggers, particularly those that cause increased oxidative stress. It is essential that the signals and associated signal transduction pathways that trigger enhanced antioxidant accumulation are elucidated as these offer an important alternative means of achieving greater nutritional value in edible plant organs. [source]

Crystallization and preliminary crystallographic analysis of bifunctional ,-glutamylcysteine synthetase,glutatione synthetase from Streptococcus agalactiae

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2009
Yasunori Nakashima
,-Glutamylcysteine synthetase,glutathione synthetase (,GCS-GS) is a bifunctional enzyme that catalyzes two consecutive steps of ATP-dependent peptide formation in glutathione biosynthesis. Streptococcus agalactiae,GCS-GS is a target for the development of potential therapeutic agents. ,GCS-GS was crystallized using the sitting-drop vapour-diffusion method. The crystals grew to dimensions of 0.3 × 0.2 × 0.2,mm under reducing conditions with 5,mM TCEP. X-ray data were collected to 2.8,Å resolution from a tetragonal crystal that belonged to space group I41. [source]

Glutathione cycle in stable chronic obstructive pulmonary disease

CELL BIOCHEMISTRY AND FUNCTION, Issue 6 2010
Biljak, Vanja Radi
Abstract Chronic obstructive pulmonary disease (COPD) is characterized by chronic inflammation and oxidant/antioxidant imbalance. Glutathione is the most abundant cellular low-molecular weight thiol and the glutathione redox cycle is the fundamental component of the cellular antioxidant defence system. Concentration of total glutathione and catalytic activities of glutathione peroxidase and glutathione reductase were determined in peripheral blood of patients (n,=,109) and healthy subjects (n,=,51). Concentration of total glutathione in patients was not changed in comparison to healthy controls. However, we found statistically significant difference between patients with moderate and severe disease stages. Glutathione reductase activity was increased, while glutathione proxidase activity was decreased in the patients with COPD, when compared to healthy controls. We found no significant difference in glutathione peroxidase and glutathione reductase activities between stages. Patients who smoked had lower concentration of total glutathione compared with former smokers and never-smoking patients. Lung function parameters were inversely associated with glutathione level. Evidence is presented for differential modulation of glutathione peroxidase and glutathione reductase activities in peripheral blood of patients with stable COPD. We suppose that in addition to glutathione biosynthesis, glutathione reductase-dependent regulation of the glutathione redox state is vital for protection against oxidative stress. Copyright © 2010 John Wiley & Sons, Ltd. [source]